Roofing underlayment

ABSTRACT

A roofing underlayment for placement over a roof substrate prior to the application of shingles, tiles or other roofing materials. The underlayment comprises a sheeting material having an upper surface and a lower surface. The underlayment contains a grid that is visually identifiable from above the underlayment when the underlayment is received over the roof substrate with its lower surface adjacent to the roof substrate. The grid assists in the alignment of the underlayment with the roofing substrate during application of the underlayment to the substrate and further assists in the alignment of roofing materials applied over the underlayment.

FIELD OF THE INVENTION

This invention relates generally to the field of roofing materials, andin particular to a new and improved roofing underlayment.

BACKGROUND OF THE INVENTION

In the construction of a pitched roof, it is highly desirable from bothan aesthetic and a functional stand point to ensure that roofingmaterials are applied in a manner so that they are “square” with theridge of the roof, and so that they are arranged in a generally parallelor “straight” configuration. For example, where asphalt shingles are tobe applied to a roof, alignment of the shingles in equally spaced rowsthat are generally horizontal and parallel to the ridge of the roofensures an aesthetically pleasing appearance and allows the shingles tofunction in the manner in which they were designed; namely, to shedwater and prevent leakage. Misalignment of shingles creates both anunattractive finished product and presents the potential for water topenetrate through the roof and into the building. Whether the exteriorroofing material is comprised of asphalt shingles, tiles, galvanized orother metallic sheeting, wooden shakes, slate or any one of a widevariety of other commonly used roofing materials, there exists a need toapply the roofing material in an aligned and “square” fashion.

To ensure the alignment of roofing materials when applied to a roofsubstrate, installation personnel typically resort to one of a varietyof common construction methods that enable subsequent rows of roofingmaterials to be aligned with previously applied rows. For example,carpenters and roofers will often mark parallel lines across the roofingsubstrate (which in wooden construction is typically plywood, exteriorwooden sheeting, or roofing boards) through the use of a pencil, markeror chalk line. In other instances the installer may use a tape measureto physically measure the distance between respective rows of roofingmaterials as each row is laid down. While both of these methods may beeffective, they are also labour intensive and introduce the potentialfor error as there is a constant requirement for individuals to takemeasurements and mark the position for subsequent rows of roofingmaterials. Failure to measure or mark accurately can result in analignment problem.

The alignment of roofing materials can be further complicated by thefact that a liner or underlayment is commonly applied to the roofsubstrate prior to the application of shingles, shakes, tiles or otherroofing materials. Such underlayments may be comprised of a wide varietyof products including roofing paper (generally comprised of a petroleumcoated cellulose product and often referred to as tar paper), roofingfelt (comprised generally of asphalt saturated organic felt which may becoated or uncoated), rubber or rubberized membranes, and an equally widevariety of synthetic underlayments (both woven and extruded). Regardlessof the particular form of underlayment that is utilized, its function isessentially the same; to provide a secondary barrier to water andmoisture beneath the shingles, tiles or other roofing materials and nextto the roof substrate. Commonly the underlayment is applied to the roofsubstrate in a series of horizontal rows and is secured to the roofthrough the use of nails, staples or an adhesive. Once applied, theunderlayment obscures the roof substrate from view making it even moredifficult for a roofer to properly align the overlying roofingmaterials.

SUMMARY OF THE INVENTION

The invention therefore provides a product and a method that allows forthe installation of shingles and other roofing materials in an alignedpattern that is “square” with the roof structure, that is costeffective, and that minimizes the potential for human error and themisalignment of roofing materials.

Accordingly, in one embodiment of the invention there is provided aroofing underlayment for placement over a roof substrate prior to theapplication of shingles, tiles or other roofing materials, theunderlayment comprising a sheeting material having an upper surface anda lower surface, said underlayment containing a grid that is visuallyidentifiable from above said underlayment when said underlayment isreceived over said roof substrate with said lower surface of saidunderlayment adjacent to said roof substrate, said grid assisting in thealignment of said underlayment with said roofing substrate duringapplication of said underlayment to said substrate and further assistingin the alignment of roofing materials applied over said underlayment.

In a further aspect the invention provides a roofing underlayment forplacement over a roof substrate prior to the application of shingles,tiles or other roofing materials, the underlayment comprising a sheetingmaterial having an upper surface and a lower surface, said underlaymentcontaining a grid that is visually identifiable from above saidunderlayment when said underlayment is received over said roof substratewith said lower surface of said underlayment adjacent to said roofsubstrate, said grid comprised of a series of equally spaced apart linesthat are parallel to the longitudinal axis of said underlayment and aseries of equally spaced apart lines that are perpendicular to thelongitudinal axis of said underlayment, said grid assisting in thealignment of said underlayment with said roofing substrate duringapplication of said underlayment to said substrate and further assistingin the alignment of roofing materials applied over said underlayment.

In yet a further aspect the invention provides a roofing underlaymentfor placement over a roof substrate prior to the application ofshingles, tiles or other roofing materials, the underlayment comprisinga sheeting material having an upper surface and a lower surface, saidunderlayment containing a grid that is visually identifiable from abovesaid underlayment when said underlayment is received over said roofsubstrate with said lower surface of said underlayment adjacent to saidroof substrate, said grid comprised of a series of spaced apart andparallel lines extending over at least a portion of said upper surfaceof said underlayment, said grid assisting in the alignment of saidunderlayment with said roofing substrate during application of saidunderlayment to said substrate and further assisting in the alignment ofroofing materials applied over said underlayment.

The invention also provides a roofing underlayment for placement over aroof substrate prior to the application of shingles, tiles or otherroofing materials, the underlayment comprising a sheeting materialhaving an upper surface and a lower surface, said underlaymentcontaining a grid that is visually identifiable when said underlaymentis received over said roofing substrate with said lower surface of saidunderlayment adjacent to said substrate, said grid comprised of a seriesof spaced apart longitudinal lines that are parallel to the longitudinalaxis of said underlayment and a series of spaced apart perpendicularlines that are perpendicular to the longitudinal axis of saidunderlayment, said longitudinal and said perpendicular lines coloured todistinguish said lines from said sheeting material.

In a further aspect the invention concerns a roofing underlayment forplacement over a roof substrate prior to the application of shingles,tiles or other roofing materials, the underlayment comprising a sheetingmaterial having an upper surface and a lower surface, said underlaymentcontaining a grid that is visually identifiable when said underlaymentis received over said roofing substrate with said lower surface of saidunderlayment adjacent to said substrate, said grid comprised of a seriesof spaced apart longitudinal lines that are parallel to the longitudinalaxis of said underlayment and a series of spaced apart perpendicularlines that are perpendicular to the longitudinal axis of saidunderlayment, said longitudinal lines being of at least a first colourcontrasting to the colour of said underlayment, said perpendicular linesbeing of at least a second colour contrasting to the colour of saidunderlayment.

Further aspects and advantages of the invention will become apparentfrom the following description taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings which show the preferredembodiments of the present invention in which:

FIG. 1 is a side sectional view through a portion of a typical pitchedroof showing one embodiment of the present invention;

FIG. 2 is an upper side perspective view of a pitched roof having aseries of horizontal rows of a roof underlayment applied thereto;

FIG. 3 is an upper perspective view of a roll of roofing underlaymentaccording to one embodiment of the present invention;

FIG. 4 is an upper perspective view of a roll of roofing underlaymentaccording to a second embodiment of the present invention;

FIGS. 5A, 5B and 5C are upper perspective views of rolls of roofingunderlayment according to a third, forth and fifth embodiment of thepresent invention;

FIG. 6 is a front view of a portion of a pitched roof showing theapplication of a roofing underlayment in accordance with a preferredembodiment of the present invention and as used in association withasphalt shingles;

FIG. 7 is a magnified detail view of a portion of a roofing underlaymentaccording to an embodiment of the present invention where theunderlayment is formed from a woven scrim;

FIG. 8 is a magnified detail side sectional view of a portion of aroofing underlayment according to an embodiment of the present inventionwhere the upper surface of the underlayment has a grid pattern embossedthereon;

FIG. 9 is a magnified detail side sectional view of a portion of aroofing underlayment according to an embodiment of the present inventionwhere the upper surface of the underlayment includes a grid patternformed from a series of tapes, yarns or filaments.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention may be embodied in a number of different forms.However, the specification and drawings that follow describe anddisclose only some of the specific forms of the invention and are notintended to limit the scope of the invention as defined in the claimsthat follow herein.

The typical structure of a standard pitched roof (as constructed in woodframed buildings) is shown in cross section in FIG. 1. In general suchroofs are comprised of a wooden substrate 1 fastened to a series oftrusses or rafters 2. A roofing underlayment 3 is commonly laid oversubstrate 1. Thereafter roofing materials 4 are applied to form thefinished roof. In most instances substrate 1 would be comprised ofplywood, exterior sheeting, or a series of wooden boards. However, itwill be appreciated that the scope and application of the presentinvention will not be limited to a particular form of substrate.Similarly, while roofing materials 4 may be comprised of asphaltshingles as shown in FIG. 1, the roofing material may equally be any oneof a wide variety of exterior roofing products, including clay or cementtiles, wooden shakes, metal roofing materials, slate, etc. As in thecase of substrate 1, the scope of the present invention is not limitedto any particular roofing material.

It is expected that in most cases underlayment 3 will be comprised of arelatively thin and flexible material formed into rolls (see FIGS. 3, 4and 5) that may be cut to length as necessary. While underlayment 3 maybe manufactured to practically any desired dimension, for handling andtransportation purposes rolls of a width of between 30 and 80 inches aremost desirable. Where rolls of this size range are utilized a series ofhorizontally oriented rows of underlayment will be applied to the roofin order to fully cover substrate 1. Preferably the rows of underlaymentmaterial are applied beginning along the lower edge of the roof workingtoward the top such that each subsequent row that is higher up on theroof overlaps the adjacent lower row to allow any moisture that may comeinto contact with the underlayment to be shed as it flows downwardlyalong the pitch of the roof. In other embodiments of the inventionsubstantially larger rolls of material could be manufactured such that asingle sheet of underlayment is capable of covering the entire exteriorsurface of substrate 1. Alternatively, the substrate could be formedinto a rigid or semi-rigid sheeting material that is applied to the roofin a manner similar to the application of the substrate material.

The composition and structure of underlayment 3 may vary substantiallydepending upon the particular application in question. The underlaymentmay range from a common tar paper or roofing felt structure, to aplastic or rubberized or PVC ice and water shield, to a single plythermoplastic (for example polyolefin) membrane, to a high strengthwoven product comprised of a series of woven tapes, yarns and/orfilaments (identified generally as 12 in FIG. 7). The underlayment mayalso be coated on one or both sides to enhance abrasion resistence, toincrease strength and water resistance, and/or to present a slipresistant surface. Depending upon the environment within which the roofstructure is located, the type of roofing material to be applied overthe underlayment, the required useful life of the roof, and consideringdifferences in costs, it may be desirable to use one particularcomposition and structure of underlayment over and above the others. Itwill be appreciated from a complete understanding of the presentinvention that the preferred embodiment of the invention is not limitedto one form of underlayment or a particular method of manufacture.

In accordance with a preferred embodiment of the invention underlayment3 is comprised of a sheeting or sheet-like material having an uppersurface 5 and a lower surface 6 that is received over roof substrate 1.Typically underlayment 3 is secured to substrate 1 through the use ofnails, staples or an adhesive. Of particular importance to the inventionis the fact that at least the upper surface 6 of underlayment 3 containsa visually identifiable grid 7. Grid 7 assists in both the alignment ofthe underlayment with the roof substrate (and with subsequent rows ofunderlayment) during application of the underlayment to the roof, andalso assists in the subsequent alignment of roofing materials that areapplied over the underlayment. It will be understood that there are avariety of manners in which grid 7 may be applied or adhered tounderlayment 3, including printing or embossing the grid upon uppersurface 6 of the underlayment. Where grid 7 is embossed on the surfaceof underlayment 3 the effect may be the formation of small linearindentations 11 across the surface of the underlayment (see FIG. 8).Grid 7 may also be printed, embossed or otherwise applied to both uppersurface 5 and lower surface 6 allowing either of the outer surfaces ofthe underlayment to be placed adjacent to roof substrate 1. Where grid 7is embossed on underlayment 3 the embossed surface will also tend toexhibit anti-skid characteristics further enhancing the characteristicsof the product.

In alternate embodiments of the invention, grid 7 may be comprised of aseries of yarns, tapes and/or filaments 10 that are woven into theunderlayment where the underlayment is a woven scrim (See generally FIG.7). The yarns, tapes and/or filaments 10 are preferably coloured acontrasting colour to the scrim and may be superimposed or adjacent tothe yarns, tapes and/or filaments 12 of the scrim. Alternatively yarns,tapes and/or filaments 10 may be otherwise adhered to either the upperand/or the lower surface of the underlayment (for example see FIG. 9)through the use of an adhesive, or during a coating process where theunderlayment is a coated product.

In one of the preferred embodiments of the invention grid 7 is comprisedof a series of equally spaced apart lines 8 that are parallel to thelongitudinal axis of the sheeting material from which the underlaymentis made (see FIG. 3). Alternately, grid 7 may be comprised of a seriesof equally spaced apart lines 9 that are perpendicular to thelongitudinal axis of the sheeting material (see FIG. 4). In yet a thirdembodiment grid 7 may be comprised of both a series of equally spacedapart lines 8 that are parallel to the longitudinal axis of the sheetingmaterial, and a series of equally spaced apart lines 9 that areperpendicular to the longitudinal axis of the sheeting material (seeFIGS. 5A, 5B and 5C).

Regardless of the particular grid structure that is used, the lines thatcomprise grid 7 must be visually identifiable, and to that extent theyare preferably of a colour other than that of the sheeting material fromwhich the underlayment is constructed (or other than the coatingmaterial where the underlayment is a coated product). For example, wherethe sheeting material of underlayment 3 is white or a light colour, grid7 may be black, green, red or some other contrasting colour making thelines of the grid clearly identifiable upon the surface of the product.In addition, the lines comprising grid 7 may in some fashion alternatein colour between a first colour and a second colour to present afurther visual identification and distinction between adjacent or groupsof lines. In these regards, one variation of grid 7 that could beutilized comprises a one inch spacing between lines that are parallel tothe longitudinal axis of the underlayment with the lines alternating incolour between green and black. In another variation, grid 7 may becomprised of lines that are parallel to the longitudinal axis of theunderlayment and that are spaced apart by one inch increments, and linesthat are perpendicular to the longitudinal axis of the underlayment andalso spaced apart in one inch increments. The longitudinally orientedlines may be black with the perpendicular lines green, presenting avisual distinction between the rows of lines that will effectively beoriented vertically and horizontally when underlayment 3 is placed in agenerally horizontal configuration across roof substrate 1. Thealternating colours of the lines forming in grid 7 helps to present avisual distinction between adjacent lines and assists in the alignmentof underlayment 3 and roofing materials 4.

Further possible variations of grid 7 are shown in FIGS. 5A and 5B. Inthe embodiment shown in FIG. 5A grid 7 is comprised of lines that areparallel to the longitudinal axis of the underlayment with adjacentparallel lines alternating in colour. The grid is further comprised oflines that are perpendicular to the longitudinal axis of theunderlayment with adjacent perpendicular lines alternating in colour.

In FIG. 5B, an embodiment is shown wherein grid 7 is comprised of aseries of lines parallel to the longitudinal axis of the underlaymentand equally spaced apart in one inch increments. The longitudinallyoriented lines alternate in colour in six inch blocks creating groups oflines of like colours that alternate every six inches. The grid furthercomprises a series of lines perpendicular to the longitudinal axis ofthe underlayment and also spaced apart in one inch increments. As in thecase of the longitudinally oriented lines, the perpendicular linesalternate in colour in six inch blocks. The grouping of theperpendicular and parallel lines in six inch blocks, and the furthersubdividing of those six inch blocks into one inch segments, has beenfound to provide the roofing installer with a visually identifiable gridthat allows for the measurement of larger distances through counting sixinch blocks, while at the same time providing for relatively precisemeasurement and alignment through reference to individual lines spacedapart in one inch increments.

It will of course be appreciated that while the embodiment depicted inFIG. 5B contemplates a line spacing of one inch with six inch groupingsin both the longitudinal and perpendicular directions, the individualline spacing, and/or the grouping of lines of a common colour, couldvary depending upon the particular end use of the product. For example,when applying particular types of roofing materials it may be desirableto use an alternate line spacing and/or an alternate grouping of linesof different colours to more closely conform to the physical dimensionsof the particular roofing materials in question. In some cases the linespacing may be as low as {fraction (1/8)} inch while in other cases aspacing as high as 24 inches may be desirable. Further, where bothvertical and horizontal lines are utilized, the spacing of thehorizontal lines maybe different than that of the vertical lines. Forexample, it may be advantageous for the horizontal lines to have anincremental spacing of one inch whereas the vertically oriented linesmay be spaced apart at intervals of 12 inches. It should also be notedthat grid 7 may be comprised of lines that are solid, broken orpatterned (for example small dots, squares, etc.).

Through the utilization of a roofing underlayment as described herein,it will be appreciated that a roofer is provided with a means by whichthe underlayment itself can be easily aligned with the roof substrate,and in particular the ridge of the roof. Where the underlayment isapplied in a series of horizontal rows, the roofing installer is able toquickly and easily align adjacent rows with one another so that theymaintain their horizontal attitude and to ensure that each subsequentrow positioned higher up on the roof is both parallel to the loweradjacent row and over laps the lower row by sufficient degree. Once theunderlayment has been applied to the roof the grid pattern that isvisually identifiable thereon presents the roofer with an ability toquickly and accurately align shingles or other roofing materials withboth one another and with the roof. An example showing how underlayment3 may be used to assist in the alignment of shingles is shown in FIG. 6.

It will thus be appreciated that utilization of underlayment 3 willremove the necessity for roofers to use chalk lines, straight edges,measuring tapes and other implements to ensure alignment of roofingmaterials as they are applied. The invention also removes the need formeasuring, and the associated potential for error in either failing tomeasure properly or failing to mark a measurement properly upon theroof. The roofer need only align the shingles or the roofing materialswith the grid pattern upon underlayment 3 to ensure that the roofingmaterials are installed in a horizontal and parallel configuration withadequate overlap. Where the underlayment exhibits anti-skidcharacteristics its application over a roof substrate will also presentan inherently safer work surface for roofing installers.

It is to be understood that what has been described are the preferredembodiments of the invention and that it may be possible to makevariations to these embodiments while staying within the broad scope ofthe invention. Some of these variations have been discussed while otherswill be readily apparent to those skilled in the art. For example, whilethe grid patterns discussed and shown in the attached Figures representwhat are believed to be some of the most likely practical embodiments ofthe invention, a variety of other grid patterns could equally beutilized, including grid patterns that are comprised of non-uniformlyspaced apart lines.

1. A roofing underlayment for placement over a roof substrate prior tothe application of shingles, tiles or other roofing materials, theunderlayment comprising a sheeting material having an upper surface anda lower surface, said underlayment containing a grid that is visuallyidentifiable from above said underlayment when said underlayment isreceived over said roof substrate with said lower surface of saidunderlayment adjacent to said roof substrate, said grid assisting in thealignment of said underlayment with said roofing substrate duringapplication of said underlayment to said substrate and further assistingin the alignment of roofing materials applied over said underlayment. 2.The underlayment as claimed in claim 1 wherein said underlayment is athin rolled material.
 3. The underlayment as claimed in claim 1 whereinsaid grid is printed on said upper surface of said underlayment.
 4. Theunderlayment as claimed in claim 1 wherein said grid is embossed on saidupper surface of said underlayment.
 5. The underlayment as claimed inclaim 1 wherein said grid is comprised of a series of equally spacedapart lines that are parallel to the longitudinal axis of saidunderlayment.
 6. The underlayment as claimed in claim 1 wherein saidgrid is comprised of a series of equally spaced apart lines that areperpendicular to the longitudinal axis of said underlayment.
 7. Theunderlayment as claimed in claim 1 wherein grid is comprised of a seriesof equally spaced apart lines that are parallel to the longitudinal axisof said underlayment and a series of equally spaced apart lines that areperpendicular to the longitudinal axis of said underlayment.
 8. Theunderlayment as claimed in claim 5 wherein adjacent lines alternate incolour between a first colour and a second colour.
 9. The underlaymentas claimed in claim 6 wherein adjacent lines alternate in colour betweena first colour and a second colour.
 10. The underlayment as claimed inclaim 7 wherein said lines that are parallel to said longitudinal axisof said underlayment are of a first colour and said lines that areperpendicular to said longitudinal axis of said underlayment are of asecond colour.
 11. The underlayment as claimed in claim 1 wherein saidsheeting material is tar paper, roofing felt, rubber, extruded plastic,woven or extruded polyolefin or PVC.
 12. The underlayment as claimed inclaim 1 wherein said sheeting material is rigid.
 13. The underlayment asclaimed in claim 1 wherein said grid is comprised of a series of yarns,tapes or filaments.
 14. The underlayment as claimed in claim 13 whereinsaid underlayment is a first colour and said yarns, tapes or filamentsare a contrasting colour.
 15. The underlayment as claimed in claim 14wherein said underlayment is a woven scrim and said yarns, tapes orfilaments are woven into said scrim.
 16. The underlayment as claimed inclaim 14 wherein said yarns, tapes or filaments are adhered to saidupper surface of said scrim.
 17. The underlayment as claimed in claim 14wherein at least said upper surface of said sheeting material is coated,said yarns, tapes or filaments embedded within said coating on saidupper surface.
 18. The underlayment as claimed in claim 1 wherein saidgrid is comprised of a series of solid, broken or patterned lines.
 19. Aroofing underlayment for placement over a roof substrate prior to theapplication of shingles, tiles or other roofing materials, theunderlayment comprising a sheeting material having an upper surface anda lower surface, said underlayment containing a grid that is visuallyidentifiable from above said underlayment when said underlayment isreceived over said roof substrate with said lower surface of saidunderlayment adjacent to said roof substrate, said grid comprised of aseries of equally spaced apart lines that are parallel to thelongitudinal axis of said underlayment and a series of equally spacedapart lines that are perpendicular to the longitudinal axis of saidunderlayment, said grid assisting in the alignment of said underlaymentwith said roofing substrate during application of said underlayment tosaid substrate and further assisting in the alignment of roofingmaterials applied over said underlayment.
 20. The underlayment asclaimed in claim 19 wherein said lines that are parallel to saidlongitudinal axis of said underlayment are of a first colour, said linesthat are perpendicular to said longitudinal axis of said underlaymentare of a second colour, and said sheeting material is of a third colour.21. A roofing underlayment for placement over a roof substrate prior tothe application of shingles, tiles or other roofing materials, theunderlayment comprising a sheeting material having an upper surface anda lower surface, said underlayment containing a grid that is visuallyidentifiable from above said underlayment when said underlayment isreceived over said roof substrate with said lower surface of saidunderlayment adjacent to said roof substrate, said grid comprised of aseries of spaced apart and parallel lines extending over at least aportion of said upper surface of said underlayment, said grid assistingin the alignment of said underlayment with said roofing substrate duringapplication of said underlayment to said substrate and further assistingin the alignment of roofing materials applied over said underlayment.22. A roofing underlayment for placement over a roof substrate prior tothe application of shingles, tiles or other roofing materials, theunderlayment comprising a sheeting material having an upper surface anda lower surface, said underlayment containing a grid that is visuallyidentifiable when said underlayment is received over said roofingsubstrate with said lower surface of said underlayment adjacent to saidsubstrate, said grid comprised of a series of spaced apart longitudinallines that are parallel to the longitudinal axis of said underlaymentand a series of spaced apart perpendicular lines that are perpendicularto the longitudinal axis of said underlayment, said longitudinal andsaid perpendicular lines coloured to distinguish said lines from saidsheeting material.
 23. The underlayment as claimed in claim 22 whereinsaid longitudinal lines are spaced apart in pre-defined increments andarranged in blocks of lines of like colour, said grid including aplurality of said blocks of longitudinal lines with adjacent blocks oflongitudinal lines alternating in colour.
 24. The underlayment asclaimed in claim 22 wherein said perpendicular lines are spaced apart inpre-defined increments and arranged in blocks of lines of like colour,said grid including a plurality of said blocks of perpendicular lineswith adjacent blocks of perpendicular lines alternating in colour. 25.The underlayment as claimed in claim 22 wherein said longitudinal linesare spaced apart in pre-defined increments and arranged in blocks oflines of like colour and said perpendicular lines are spaced apart inpre-defined increments and arranged in blocks of lines of like colour,said grid including a plurality of said blocks of longitudinal lines anda plurality of said blocks of perpendicular lines, said adjacent blocksof longitudinal lines alternating in colour and said adjacent blocks ofperpendicular lines alternating in colour.
 26. A roofing underlaymentfor placement over a roof substrate prior to the application ofshingles, tiles or other roofing materials, the underlayment comprisinga sheeting material having an upper surface and a lower surface, saidunderlayment containing a grid that is visually identifiable when saidunderlayment is received over said roofing substrate with said lowersurface of said underlayment adjacent to said substrate, said gridcomprised of a series of spaced apart longitudinal lines that areparallel to the longitudinal axis of said underlayment and a series ofspaced apart perpendicular lines that are perpendicular to thelongitudinal axis of said underlayment, said longitudinal lines being ofat least a first colour contrasting to the colour of said underlayment,said perpendicular lines being of at least a second colour contrastingto the colour of said underlayment.